Healthy Living

What Is the Cause of an Underactive Thyroid Gland?

What is the Cause of an Underactive Thyroid Gland?

Gaining weight? Feeling colder? Feeling depressed? Hypothyroidism could be the reason behind it.

What is hypothyroidism?

Also known as low thyroid or underactive thyroid, hypothyroidism is characterized by underactive thyroid glands that fail to produce an adequate amount of thyroid hormones. These hormones are important in maintaining the body's metabolic rate and energy production. Thus, low levels of thyroid hormones affect each and every organ of the body, making the person totally exhausted or weak. It is very common in the population and affects millions.

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Who are affected by hypothyroidism?

People of any age may be affected by hypothyroidism. However, it is more common among elderly people, particularly, women above 50 years of age. The risk of hypothyroidism increases with its presence in one's family history.

What causes hypothyroidism?

The inability of the thyroid gland to produce adequate amounts of certain hormones results in hypothyroidism. Your pituitary gland may also lead to hypothyroidism when it fails to stimulate the thyroid glands to produce enough of the thyroid-stimulating hormone (TSH). In some other cases, an insufficient production of the thyrotropin-releasing hormone (TRH) from the hypothalamus causes inadequate stimulation of the pituitary, which in turn affects the production of thyroid hormones in the thyroid glands. Iodine deficiency is the most important cause of hypothyroidism worldwide. In countries where people's iodine intake is sufficient, Hashimoto’s thyroiditis is the most common result of the deficiency. In Hashimotos' thyroiditis, the immune system destroys the tissues of the thyroid gland. The surgical removal of the thyroid gland and radiation therapy for cancer may also lead to hypothyroidism.

What are the symptoms of hypothyroidism?

Feelings of exhaustion, sensitivity to cold, constipation, forgetfulness, irregular menstrual periods, brittle nails, and skin dryness are the most common symptoms of hypothyroidism. These symptoms usually develop gradually over a period of time. However, many sufferers often ignore these symptoms and erroneously account them to aging. One should remember to consult a physician when such symptoms persist.

How is hypothyroidism diagnosed?

The first steps in the diagnosis of hypothyroidism are an evaluation of the patient's medical history and a thorough physical examination. If hypothyroidism is suspected, the doctor will recommend blood tests to confirm the diagnosis. The tests used to confirm the condition are TSH (thyroid-stimulating hormone) and T4 (thyroxine) tests.

If the above-mentioned tests are normal, the doctor may suggest thyroid antibody tests to check for Hashimoto’s disease. In some rare cases, an ultrasound scan of the thyroid gland might be suggested. A computerized tomography (CT) scan or magnetic resonance imaging (MRI) is used to assess the brain's pituitary gland and hypothalamus.

How is hypothyroidism treated?

When left untreated, hypothyroidism can lead to an increase in blood cholesterol levels, which is a major risk factor for developing heart diseases. Hypothyroidism during pregnancy can harm the developing fetus as well. In children, hypothyroidism may result in intellectual disability. Hence, treatment of hypothyroidism is very important.

The most common treatment 

To treat hypothyroidism, hormone therapy using synthetic thyroid hormone, levothyroxine is prescribed. The appropriate dosage for each person may differ depending on individual needs. Appropriate amounts of the hormone are important as either deficiency and excess may cause symptoms. The initial dosage is often started off lower in patients with heart diseases and then increased gradually so as to allow the heart to adjust to the increased metabolic rate.

Hormone replacement 

An improvement in one's symptoms is felt within a few weeks of hormone replacement, and complete relief comes after a few months of treatment. The response may be delayed in elderly people and in patients with other medical conditions. Normal thyroid gland function may be restored in patients with Hashimoto’s disease after some time, even without any specific treatment. Treating any infections and avoiding any medications that can cause hypothyroidism can also help restore the normal functioning of the thyroid gland.


With hypothyroidism affecting 4.6 percent of the U.S. population, especially ages 12 and older (although most cases are mild), it is critical to get the facts right to get correct information, diagnosis, and treatment.


The general symptoms include fatigue, constipation, cold sensitivity, unexplained weight gain, and dry skin. The disorder affects the whole body, causing problems with sleep, menstruation, the gastrointestinal system, muscles, hair, and mood.

Common causes

The most common cause of the disorder is an autoimmune condition called as "Hashimoto’s thyroiditis", which is also known as "Hashimoto's disease". This disease is a type of inflammation in the thyroid gland caused by the immune system. Apart from the autoimmune predisposition, surgical removal of the thyroid gland, radiation treatment, congenital factors, certain medications, iodine imbalance, radiation treatment, and damage to the pituitary gland can cause hypothyroidism.

Risk factors

Even babies and children are prone to the disorder, but the condition is most commonly observed in women over 50 years of age.


The disease can be detected by blood tests. The TSH (thyroid-stimulating hormone) test is the blood test that detects the amount of T4 hormone, which the thyroid gland is producing. This test can also determine the amount of T4 the thyroid is being signaled to produce.


Many drugs and medicines can affect the functions of the thyroid gland. The medications cannot cure the condition but can keep the thyroid levels in control for the rest of a person's life. It is easier to boost the degree of thyroid hormone with medicines as they normally do not cause any side effects if taken in the right doses.

T4 supplements

T3 is the more active hormone between the two major hormones produced by the thyroid gland. T4 supplements are used to treat the disorder because the T3 in our blood were once T4 before losing an iodine atom to interact with the cells. 


If treated correctly, hypothyroidism shows a good prognosis and its symptoms are greatly reduced or eliminated. If left untreated, however, the disorder can lead to serious complications, particularly heart disorders. It can also be accompanied by the risk of developing osteoporosis, anorexia, myxedema, increased chances of miscarriage during pregnancy, and other fatal problems.


There are no preventive measures for hypothyroidism, and it stays with the patient for life. The best that can be done is knowing about the risk factors, recognizing the signs and symptoms at the earliest time, and getting the right diagnosis as well as proper and efficient treatment as soon as possible. Once you have been diagnosed and prescribed medication, you must ensure that you maintain a hormone replacement therapy, and go for periodic checkups monitoring your thyroid hormone levels, since hormone replacement dosage may sometimes need to be adjusted. 

There is no guaranteed way to prevent hypothyroidism, but getting correctly diagnosed as soon as possible and following a well-controlled treatment regimen prescribed by a good endocrinologist will give you the quickest relief and allow you to live your life without suffering from any symptoms and risking complications.